# The Naked Scientists Forum

### Author Topic: Speed Of Sound In Neutron Stars.  (Read 6163 times)

#### Titanscape

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##### Speed Of Sound In Neutron Stars.
« on: 06/01/2005 14:38:10 »
Can sound in a Neutron star travel faster than light? For it is so dense. Sound would be like kinetic energy in that big nucleus.

Titanscape

#### gsmollin

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##### Re: Speed Of Sound In Neutron Stars.
« Reply #1 on: 07/01/2005 20:26:35 »
No mass or energy may propagate faster than c, the speed of light in vacuo. It may exceed the local speed of light in a given medium, such as the relativistic electrons in water radiating blue light.

Remember sound waves are moving matter, so no, it won't happen.

#### Titanscape

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##### Re: Speed Of Sound In Neutron Stars.
« Reply #2 on: 08/01/2005 15:35:41 »
Good point, I had never put this in perspective before. Imagine a dense rod in space like a diamond formed inside pressures of Jupiter's core. If it were 1 light minute long and pushed on one side, are you saying that the other side would take more than 1 minute to respond?

Titanscape
« Last Edit: 08/01/2005 15:38:33 by Titanscape »

#### qpan

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##### Re: Speed Of Sound In Neutron Stars.
« Reply #3 on: 08/01/2005 20:52:04 »
That is a great question titanscape. The only thing is a 1 minute long rod is pretty long - its actually quite hard to imagine the scenario (1/8th the distance to the sun in fact). However, unless the rod was infinitely hard, it would need to temporarily compress before moving, and therefore it would take significantly longer than 1 minute to respond at the other end. Although this seems illogical, it is due to the lengths involved - the rod would only need to compress by 5.5594E-09% in order to be compressed by 1m.

"I have great faith in fools; self-confidence my friends call it."
-Edgar Allan Poe

#### Ultima

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##### Re: Speed Of Sound In Neutron Stars.
« Reply #4 on: 11/01/2005 19:48:47 »
what would happen assuming infinite stiffness and hardness?

wOw the world spins?

#### neilep

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##### Re: Speed Of Sound In Neutron Stars.
« Reply #5 on: 11/01/2005 19:53:35 »
quote:
Originally posted by Ultima

what would happen assuming infinite stiffness and hardness?

wOw the world spins?

well...first you have to get an infinite supply of Viagra .....ok....I'm ready to ban myself !![:o)]

'Men are the same as women...just inside out !'

#### gsmollin

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##### Re: Speed Of Sound In Neutron Stars.
« Reply #6 on: 26/01/2005 23:07:21 »
I had the same thought when I read the question, but neilp was there first!

Infinities are a real problem. With infinite, er, stiffness, the speed of sound would be infinite, but how do you produced a sound in a medium with infinite stiffness?

#### The Naked Scientists Forum

##### Re: Speed Of Sound In Neutron Stars.
« Reply #6 on: 26/01/2005 23:07:21 »